The present invention relates generally to medical devices and methods for making same. More specifically, the invention relates to implantable medical devices having at least one porous layer, and methods for making such devices.
Implantable medical devices are increasingly being used to deliver one or more therapeutic agents to a site within a body. Such agents may provide their own benefits to treatment and/or may enhance the efficacy of the implantable device. For example, much research has been conducted into the use of drug eluting stents for use in percutaneous transluminal coronary angioplasty (PTCA) procedures. Although some implantable devices are simply coated with one or more therapeutic agents, other devices include means for containing, attaching or otherwise holding therapeutic agents to provide the agents at a treatment location over a longer duration, in a controlled-release manner, or the like.
Porous materials, for example, are commonly used in medical implants as matrices for the retention of therapeutic agents. Materials that have been used for this purpose include ceramics such as hydroxyapatites and porous alumina, as well as sintered metal powders. Polymeric materials such as poly(ethylene glycol)/poly(L-lactic acid) (PLGA) have also been used for this purpose. These materials are typically applied as coatings to the medical implant, raising issues regarding coating adhesion, mechanical properties, and material biocompatibility. Further, application of these coatings introduces additional complexity to the fabrication process, increasing overall production costs.
Therefore, it would be advantageous to have improved implantable medical devices with porous layers and methods for fabricating those devices. Such methods would ideally produce a more adherent and mechanically robust porous layer while simplifying device manufacture. Methods would also ideally provide porous layers having desired pore sizes and densities. At least some of these objectives will be met by the present invention.